The present disclosure relates to an image forming apparatus that performs image processing based on image data.
An image forming apparatus such as a printer, copy machine, multifunction peripheral and the like is equipped with an ASIC (Application Specific Integrated Circuit) prepared according to the size of an original processed by the image forming apparatus.
For example, an image forming apparatus that can feed paper of no larger than an A4-size (A4 apparatus) is equipped with an ASIC prepared to correspond to a paper width of the A4 paper as an image processing width. In addition, an image forming apparatus that can feed paper of no larger than an A3-size (A3 apparatus) is equipped with an ASIC prepared to correspond to a paper width of the A3 paper as an image processing width.
An image forming apparatus can realize cost-effectiveness by employing an ASIC prepared for each supported original size.
In addition, upon output of image data that is read by scanning an original, the image forming apparatus generates a halftone image by a halftone process and adjusts density of the image to be formed by area coverage modulation such as the dither method and the error diffusion method. The halftone process by the dither method or the like, which is performed by a comparatively simple algorithm, is realized by the ASIC.
Here, from a viewpoint of development of various models, an idea of shared use of a module should be promoted not only in a software field but also in a hardware field. Especially, regarding the ASIC, there is a demand for compatibility with an A4 machine and an A3 machine, with a reduced cost. Given this, a software control method and the like that allows use of the ASIC for A4 machine in the A3 machine has been desired.
In a case of using the ASIC for A4 machine in the A3 machine, the following problems may occur.
For example, in a conventional A4 machine, the halftone process is realized by the configuration shown in FIG. 11.
In other words, in conventional image forming apparatus 100, the image data after a rotational process by image rotation unit 110 is stored as band data corresponding to each color of CMYK, in each of 4-channel band buffers 120-1 to 120-4.
Halftone processing unit 130 is capable of processing band data in 4 channels in parallel. Halftone processing unit 130 performs the halftone process by fetching the band data of each color stored in each of 4-channel band buffers 120-1 to 120-4.
And then, the image data after the halftone process is stored as band data corresponding to each color of CMYK, in each of 4-channel band buffers 140-1 to 140-4. The stored band data transmitted to printing engine control unit 150 for printing output.
Using the ASIC for A4 machine in an A3 machine causes the following problem.
In other words, among ASIC modules for the A4 machine, a module for the halftone process only supports a main scan control width of up to 5120 dots (approximately 216.7 mm) due to limited circuit size of the ASIC. Therefore, image data with a width of A3-size original (297 mm) cannot be processed by the ASIC.
As a result, using the ASIC for A4 machine in an A3 machine does not allow processing of an A3-sized original.